Rendering wide color gamut, two-dimensional (2D) images on three-dimensional (3D) capable displays

ABSTRACT

A system and method for displaying image data comprise receiving 2D video data, generating, from the video data, a first plurality of intensity values of virtual primaries of a first virtual color gamut and a second plurality intensity values of a second virtual color gamut, the first plurality of intensity values being below a luminance threshold and approximating a predefined color gamut and the second plurality of intensity values being above the luminance threshold, converting the first plurality of intensity values into a third plurality of intensity values of predefined primaries of a first projection head of a display system and the second plurality of intensity values into a fourth plurality of intensity values of predefined primaries of a second projection head of the display system, and dynamically adjusting pixel levels of spatial modulators of the display system based on the third plurality and the fourth plurality of intensity values.

BACKGROUND Field of the Disclosure

This application relates generally to the rendering of wide color gamutimages.

Description of Related Art

Displays capable of displaying three-dimensional (3D) images may displaya left eye image and a right eye image using two distinct sets ofprimaries (6P) which, when viewed together, give the appearance of a 3Dimage. Such displays may also be utilized to display two-dimensional(2D) images.

SUMMARY OF THE DISCLOSURE

Various aspects of the present disclosure relate to systems and methodsfor improved rendering of two 2D images on 6P 3D projectors and displaysystems (in particular, spectral separation 3D projectors and displaysystems).

In one exemplary aspect of the present disclosure, there is provided adual-head projection system comprising a first projection head, a secondprojection head, at least one spatial modulator, and an electronicprocessor. The electronic processor is configured to receive 2D videodata, generate, from the video data, a first plurality of intensityvalues of virtual primaries of a first virtual color gamut and a secondplurality intensity values of virtual primaries of a second virtualcolor gamut, the first plurality of intensity values being below aluminance threshold and approximating a predefined color gamut and thesecond plurality of intensity values being above the luminancethreshold, convert the first plurality of intensity values into a thirdplurality of intensity values of predefined primaries of the firstprojection head and the second plurality of intensity values into afourth plurality of intensity values of predefined primaries of thesecond projection head, and dynamically adjust pixel levels of thespatial modulators of the first projection head and the secondprojection head.

In another exemplary aspect of the present disclosure, there is provideda method for displaying image data. The method comprises receiving 2Dvideo data, generating, from the video data, a first plurality ofintensity values of virtual primaries of a first virtual color gamut anda second plurality intensity values of a second virtual color gamut, thefirst plurality of intensity values of the first virtual color gamutbeing below a luminance threshold and approximating a predefined colorgamut and the second plurality of intensity values being above theluminance threshold, converting the first plurality of intensity valuesinto a third plurality of intensity values of predefined primaries of afirst projection head of a display system and the second plurality ofintensity values into a fourth plurality of intensity values ofpredefined primaries of a second projection head of the display system,and dynamically adjusting pixel levels of spatial modulators of thefirst and second projection heads of the display system based on thethird plurality of intensity values and the fourth plurality ofintensity values.

In another exemplary aspect of the present disclosure, there is provideda method for displaying image data. The method comprises receiving videodata, generating, based on an intensity level of the video data, a firstplurality of intensity values associated with the first virtual colorgamut, generating, based on a comparison between the intensity level andat least one predetermined threshold, a second plurality of intensityvalues associated with the second virtual color gamut, generating, basedon the first plurality and the second plurality of intensity values, athird plurality of intensity values and a fourth plurality of intensityvalues associated with the plurality of primary display colors, andproviding the third plurality of intensity values and the fourthplurality of intensity values to at least one spatial light modulator.

In another exemplary aspect of the present disclosure, there is provideda non-transitory computer-readable medium storing instructions that,when executed by a processor of a computer, cause the computer toperform operations comprising receiving 2D video data includingtristimulus pixel values of predefined primaries of a predefined colorspace, generating, from the video data, a first plurality of intensityvalues of virtual primaries of a first virtual color gamut and a secondplurality intensity values of a second virtual color gamut toapproximate a predefined color gamut, the first plurality of intensityvalues being below a luminance threshold of the first virtual colorgamut and the second plurality of intensity values being above theluminance threshold, converting, via a blending function, the firstplurality of intensity values into a third plurality of intensity valuesof the predefined primaries and the second plurality of intensity valuesinto a fourth plurality of intensity values of the predefined primaries,and dynamically adjusting pixel levels of at least one spatial modulatorof a dual-head projection system based on the third plurality ofintensity values and the fourth plurality of intensity values.

In this manner, various aspects of the present disclosure provide forthe rendering of 2D images from a 3D projection device, and improvementsin at least the technical fields of image projection, signal processing,and the like.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, together with the detailed description below, are incorporated inand form part of the specification, and serve to further illustrateembodiments of concepts, and explain various principles and advantagesof those embodiments.

FIG. 1A is a spectrum diagram of a 6P projection system according tovarious aspects of the present disclosure.

FIG. 1B is a block diagram of a projection system according to variousaspects of the present disclosure.

FIG. 1C is a block diagram of a projection system according to variousaspects of the present disclosure.

FIG. 2 is a block diagram of a controller included in the system ofFIGS. 1B and 1C according to various aspects of the present disclosure.

FIG. 3 is flowchart illustrating a method implemented by the controllerof FIG. 2 according to various aspects of the present disclosure.

FIG. 4 is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 5A is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 5B is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 6A is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 6B is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 7A is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 7B is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 8A is a chromaticity diagram according to various aspects of thepresent disclosure.

FIG. 8B is a chromaticity diagram according to various aspects of thepresent disclosure.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present disclosure.

The apparatus and method components have been represented whereappropriate by symbols in the drawings, showing only those specificdetails that are pertinent to understanding the embodiments of thepresent disclosure so as not to obscure the disclosure with details thatwill be readily apparent to those of ordinary skill in the art havingthe benefit of the description herein.

DETAILED DESCRIPTION

As previously mentioned, some 6P displays configured to project 3Dimages may be utilized to project/display 2D images. When projecting 3Dimages, the six primaries are used to display the left-eye and right-eyeimages using one set of three (red, green, and blue) primaries for theleft-eye image and the other set of three primaries for the right-eyeimage. 3D glasses for use with such a display may have correspondingfilters (such as band pass filters) to allow each eye to see theappropriate image. Two-dimensional images can be displayed by 3Ddisplays by driving each pair of primary light sources with the samedata without the need to for a viewer to wear 3D glasses. For example,the 2D red data values are used to drive both the red1 and the red2primaries. Similarly, the 2D green data values are used to drive boththe green1 and the green2 primaries, and the 2D blue data values areused to drive both the blue1 and blue2 primaries. The system iscalibrated with the combined primaries and images can be produced.However, the resulting color gamut can be limited significantly withrespect to a desired color gamut (for example, the established Rec 2020gamut).

This disclosure and aspects thereof can be embodied in various forms,including hardware or circuits controlled by computer-implementedmethods, computer program products, computer systems and networks, userinterfaces, and application programming interfaces; as well ashardware-implemented methods, signal processing circuits, memory arrays,application specific integrated circuits, field programmable gatearrays, and the like. The foregoing summary is intended solely to give ageneral idea of various aspects of the present disclosure, and does notlimit the scope of the disclosure in any way.

In the following description, numerous details are set forth, such ascircuit configurations, waveform timings, circuit operations, and thelike, in order to provide an understanding of one or more aspects of thepresent disclosure. It will be readily apparent to one skilled in theart that these specific details are merely exemplary and not intended tolimit the scope of this application.

Moreover, while the present disclosure focuses mainly on examples wherethe received video data is of Rec2020, it will be understood that thisis merely one example of an implementation and that other color spacedmay be utilized. It will further be understood that the disclosedsystems and methods can be used in any projection system to improve therendering of 2D images on six primary displays.

For ease of description, some or all of the example systems presentedherein are illustrated with a single exemplar of each of its componentparts. Some examples may not describe or illustrate all components ofthe systems. Other example embodiments may include more or fewer of eachof the illustrated components, may combine some components, or mayinclude additional or alternative components. For example, in someembodiments the system 100 of FIGS. 1B and 1C below includes more thanone light source 102.

As described above, some 3D displays, referred to as 6P systems,simultaneously display a left eye and right eye image using two distinctsets of primaries. FIG. 1A is a spectral diagram 1 of a 6P system inaccordance with some embodiments. The diagram 1 includes three shortwavelengths 2A, 3A, and 4A (referred to herein as short primaries) andthree long wavelengths 2B, 3B, and 4B (referred to herein as longprimaries). The example display systems described herein are configuredto utilize the short primaries 2A, 3A, and 4A for the left eye image(for example, via a designated left projector) and the long primaries2B, 3B, and 4B for the right eye image (for example, via a designatedright projector). It should be understood that, in further embodiments,a combination of short and long primaries may be utilized for each eyeimage. As explained in more detail below, each projector outputs amodulated light output (of the designated primaries of the projector)onto a display or viewing screen. In the embodiments described herein,both the left eye image and the right eye image are simultaneouslydisplayed.

FIGS. 1B and 1C are each a block diagram of exemplary display systems100 in accordance with some embodiments. Each system includes at leastsome similarly configured components, which are labelled as such. Thedisplay system 100 is configured to display 3D and 2D video datareceived from a video data source 101. The display system 100 may be anykind of system configured to display images, for example, a projectionsystem or a light-emitting diode (LED) display system. The displaysystem 100 includes a light source 102, illumination optics 104, aseparator 106, one or more modulators 108, a combiner 110, projectionoptics 112, and a controller 114. While FIGS. 1B and 1C illustrate onelight source 102, display systems 100 in accordance with someembodiments may contain multiple light sources 102. The components ofthe system 100 may be housed in a single projection device (such as asingle projector) or, in some embodiments, multiple devices. Forexample, in some embodiments, the light sources, the modulators, andother components of the display system 100 can be separated into two ormore separate, coordinated projection devices.

The light source 102 is driven by the controller 114 to produce anillumination beam including, in the illustrated embodiment, six primarycolors. The illumination beam is directed through illumination optics104 and into color separator 106. The color separator 106 separates theillumination beam into the six primary beams and directs each primarybeam to an associated one of spatial light modulators (SLMs) 108. Eachmodulator 108 modulates the primary illumination beams based on inputfrom the controller 114, as described in more detail below. Theprojection optics 112 focus the modulated beam to form an imaging beam116. The imaging beam 116 is then projected to create an image, forexample, onto a viewing surface (not shown). In the exemplary system ofFIG. 1B, the left- and right-eye images may be alternatingly projected(also called “time divisional multiplexing”).

In some embodiments, each primary color may be associated with anindividual modulator 108. Alternatively, as shown in FIG. 1B, the numberof modulators may be reduced, for example by using a field sequentialmodulation scheme. In some embodiments, the modulators can include aplurality of modulators for each primary color, as, for example, in adual modulation projector. In some embodiments, each modulator 108 isassociated with a set of primary colors. For example, as described abovein regard to FIG. 1A, a 6P system, as shown in FIG. 1C, may include aleft projector and a right projector. FIG. 1C illustrates a dual headdisplay system 100, which includes separate modulators 108A and 108B,projection optics 112A and 112B, and two resulting imaging beams 116Aand 116B, each set of which are designated for a left eye channel and aright eye channel respectively. The modulator 108A, projection optics112A, and the resulting imaging beam 116A may be considered componentsof a left projector (projection head) and the modulator 108B, projectionoptics 112B, and the resulting imaging beam 116B may be consideredcomponents of a right projector (projection head). As described above,light outputs from both channels are shown simultaneously to produce asingle resulting image on a display or screen. Furthermore, while FIGS.1B and 1C illustrate video data source 101 as being separate from thedisplay system 100, in some embodiments the video data source 101 may beinternal to the display system 100 (for example, in a memory associatedwith the display system 100).

FIG. 2 is a block diagram of the controller 114 in accordance with someembodiments. The controller 114 includes an electronic processor 205, amemory 210, and an input/output interface 215. The electronic processor205 obtains and provides information (for example, from the memory 210and/or the input/output interface 215), and processes the information byexecuting one or more software instructions or modules, capable of beingstored, for example, in a random access memory (“RAM”) area of thememory 210 or a read only memory (“ROM”) of the memory 210 or anothernon-transitory computer readable medium (not shown). The software caninclude firmware, one or more applications, program data, filters,rules, one or more program modules, and other executable instructions.The electronic processor 205 may include multiple cores or individualprocessing units. The electronic processor 205 is configured to retrievefrom the memory 210 and execute, among other things, software related tothe control processes and methods described herein.

The memory 210 can include one or more non-transitory computer-readablemedia, and includes a program storage area and a data storage area. Theprogram storage area and the data storage area can include combinationsof different types of memory, as described herein. The memory 210 maytake the form of any non-transitory computer-readable medium.

The input/output interface 215 is configured to receive input and toprovide system output. The input/output interface 215 obtainsinformation and signals from, and provides information and signals to(for example, over one or more wired and/or wireless connections)devices both internal and external to the display system 100, forexample, the light source 102, the modulator(s) 108, and the video datasource 101.

FIG. 3 is a flowchart illustrating an example method 300 of operating aprojection system in accordance with some embodiments. As an example,the method 300 is described as being performed by the controller 114illustrated in FIGS. 1B and 1C and, in particular, the electronicprocessor 205 illustrated in FIG. 2.

At block 302, the electronic processor 205 receives video data from avideo data source, such as the video data source 101 illustrated inFIGS. 1B and 1C. The video data may include a series of tristimuluspixel values from a video content stream or file. In some embodiments,the video data includes pixel values in a color space (or gamut) such asRec2020 (also referred to as ITU-R Recommendation BT.2020). At block304, the electronic processor 205 generates, from the video data, afirst plurality of intensity values of virtual primaries of a firstcolor gamut and, at block 306, generates, from the video data, a secondplurality of intensity values of virtual primaries of a second colorgamut. In particular, a gamut volume for 2D images is split into twovirtual gamuts: gamut A and gamut B. Each gamut includes virtualprimaries that are specific blends of the predefined primaries. Asexplained in more detail below, gamut A is optimized to be as close to apredefined color gamut, for example a defined standard color space (forexample, Rec2020), while gamut B is utilized for any residual energyfrom the predefined primaries. In other words, gamut A is used for lowerluminance levels and gamut B is added to achieve higher luminance levelswhen applicable. In some embodiments, gamut A is optimized to achievethe largest possible color gamut.

Returning to FIG. 3, at block 308, the electronic processor 205 convertsthe first plurality of intensity values into a third plurality ofintensity values of predefined primaries of a first eye channel (forexample, a channel of a first projection head) and the second pluralityof intensity values into a fourth plurality of intensity values ofpredefined primaries of a second eye channel (for example, a channel ofa second projection head).

In some embodiments, a blending function is applied to gamut A and gamutB to optimize each gamut to be close to the color space of the videodata (in the present example, Rec2020). In other words, in theseembodiments, the electronic processor 205 converts, e.g. via one or moreblending function, the first plurality of intensity values and thesecond plurality of intensity values into a third plurality of intensityvalues of predefined primaries of a first eye channel (for example, achannel of a first projection head). The electronic processor 205 alsoconverts, e.g. via one or more blending function, the first plurality ofintensity values and the second plurality of intensity values into afourth plurality of intensity values of predefined primaries of a secondeye channel (for example, a channel of a second projection head).Equations [1] and [2] below illustrate the blending function performedat block 308 for the left eye channel and the right eye channelrespectively.

$\begin{matrix}{\begin{bmatrix}R_{L} \\G_{L} \\B_{L}\end{bmatrix} = {{\left\lbrack B_{AL} \right\rbrack\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix}} + {\left\lbrack B_{BL} \right\rbrack\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix}}}} & \lbrack 1\rbrack \\{and} & \; \\{\begin{bmatrix}R_{S} \\G_{S} \\B_{S}\end{bmatrix} = {{\left\lbrack B_{AS} \right\rbrack\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix}} + {\left\lbrack B_{BS} \right\rbrack\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix}}}} & \lbrack 2\rbrack\end{matrix}$

The matrix of R_(L) G_(L) B_(L) corresponds to the third plurality ofintensity values, e.g. primaries of the right eye channel, and thematrix of R_(S) G_(S) B_(S) corresponds to the fourth plurality ofintensity values, e.g. primaries of the left eye channel, in which Rrefers to a red primary, G refers to a green primary, B refers to a blueprimary, the subscript L refers to “long” wavelength primaries, and thesubscript S refers to “short” wavelength primaries. In some embodiments,the right eye channel may include the short wavelength primaries whilethe left eye channel includes the long wavelength primaries. In bothequations, gamut A (the matrix including R_(A) G_(A) B_(A)) and gamut B(the matrix including R_(B) G_(B) B_(B)) of each channel is scaled by ablend matrix (the matrices of B_(AL), B_(BL), B_(AS), and B_(BS)). Theparticular values of the blend matrices may be predetermined valuesdetermined based on the location of the primaries and the predeterminedcolor space. The particular values may also be dependent on theprojection/display system used (for example, the type of projectorhead). Example methods of determination of each blend matrices aredescribed in more detail below. In the present example, the followingblend matrices values are used:

$\left\lbrack B_{AL} \right\rbrack = {{\begin{bmatrix}0 & 0 & 0 \\0.0096 & 0.2626 & 0 \\0 & 0 & 0.9733\end{bmatrix}\left\lbrack B_{BL} \right\rbrack} = {{\begin{bmatrix}1.0000 & 0 & 0 \\0 & 0.7278 & 0 \\0 & 0 & 0.0267\end{bmatrix}\left\lbrack B_{AS} \right\rbrack} = {{\begin{bmatrix}0.9904 & 0 & 0 \\0 & 0.7374 & {0{.0267}} \\0 & 0 & 0\end{bmatrix}\left\lbrack B_{BS} \right\rbrack} = \begin{bmatrix}0.0096 & 0 & 0 \\0 & 0.2359 & 0 \\0 & 0 & 1.0000\end{bmatrix}}}}$

Returning to FIG. 3, at block 310, the electronic processor 205dynamically adjusts pixel levels of at least one spatial modulator, suchas the modulator 108 illustrated in FIGS. 1B and C, based on the thirdplurality of intensity values and the fourth plurality of intensityvalues. In embodiments where the system 100 is a dual head projectionsystem, pixel levels of the modulator of each of the projection headsare adjusted.

As mentioned above, gamut A is optimized to be as close to a predefinedcolor gamut, for example a defined standard color space (for example,Rec2020), while gamut B is utilized for any residual energy from thepredefined primaries. Below two exemplary methods implemented by theprocessor 205 to process received video data into gamuts A and B aredescribed.

One method to optimize gamut A is by scaling (compressing) thechromaticities of the video data to fit within the achievable gamutvolume of the light source 102, referred to herein as gamut scaling. Inthe gamut scaling method, two functions are defined:f _(l)(C)=if(C<0.5),C,else 0.5f _(u)(C)=C−f _(l)(C)C∈R ₂₀₂₀ ,G ₂₀₂₀ ,B ₂₀₂₀

The variable C represents the pixel values of the received video data,which is here assumed to be tristimulus Rec2020 data. The functionf_(l)(C) represents a lookup table for gamut A while the functionf_(u)(C) represents a lookup table for gamut B. In the present example,the function f_(l)(C) defines a linear ramp increasing from 0 to 0.5 andflat-lining beyond 0.5 while the function f_(u)(C) defines a flat linefrom 0 to 0.5 and a linear ramp increasing from 0.5. The value 0.5corresponds to a luminance threshold. In some embodiments, a differentluminance threshold may be used.

For each of the pixel values of the received video data, gamut A andgamut B are derived as follows:

$\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix} = {{\begin{bmatrix}{f_{l}\left( R_{2020} \right)} \\{f_{l}\left( G_{2020} \right)} \\{f_{l}\left( B_{2020} \right)}\end{bmatrix}\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix}} = \begin{bmatrix}{f_{u}\left( R_{2020} \right)} \\{f_{u}\left( G_{2020} \right)} \\{f_{u}\left( B_{2020} \right)}\end{bmatrix}}$

In other words, for each primary channel of the incoming video dataR₂₀₂₀, G₂₀₂₀, and B₂₀₂₀, the pixel values with a luminance level under0.5 (corresponding to 50% of the total luminance range of the system 100and 100% of the luminance range of gamut A) are included within gamut Awhile the pixel values that exceed 0.5 (meaning that they are outside ofthe luminance range of gamut A) are allocated to gamut B. The derivedgamut A and gamut B signals are then converted to the defined primariesas described above in regard to block 308 and equations 1 and 2.

Another method to process received video data into gamut A is byclipping chromaticities to fit within gamuts A and B to fit within theachievable gamut volume of the light source 102. First, thetransformation relationship [C]_(A) and [C]_(B) from the color space ofthe source 102 to gamut A and gamut B, respectively, is defined. Thederivation may be performed as follows.

Knowing the normalized primary matrices for the left channel and rightchannel, arbitrary points in both channels may be defined as:

$\begin{bmatrix}X \\Y \\Z\end{bmatrix} = {{\left\lbrack {NPM} \right\rbrack_{LLL}\begin{bmatrix}R_{L} \\G_{L} \\B_{L}\end{bmatrix}} + {\left\lbrack {NPM} \right\rbrack_{SSS}\begin{bmatrix}R_{S} \\G_{S} \\B_{S}\end{bmatrix}}}$

Where the matrix of X, Y, and Z corresponds to an arbitrary point, thematrices of NPM_(LLL) and NPM_(SSS) correspond to the normalized primarymatrices of the right eye channel and the left eye channel respectively,and the matrices of R_(L), G_(L), and B_(L) and R_(S), G_(S), and B_(S)correspond to non-normalized matrices of the right eye channel and theleft eye channel respectively.

The blending functions defined in equations 1 and 2 above are eachsubstituted in as the non-normalized matrices of the right eye channeland the left eye channel respectively.

$\begin{bmatrix}X \\Y \\Z\end{bmatrix} = {{\left\lbrack {NPM} \right\rbrack_{LLL}\left\{ {{\left\lbrack B_{AL} \right\rbrack\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix}} + {\left\lbrack B_{BL} \right\rbrack\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix}}} \right\}} + {\left\lbrack {NPM} \right\rbrack_{SSS}\left\{ {{\left\lbrack B_{AS} \right\rbrack\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix}} + {\left\lbrack B_{BS} \right\rbrack\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix}}} \right\}}}$

Converting the above formula into terms of primary matrices, the formulabecomes:

$\begin{bmatrix}X \\Y \\Z\end{bmatrix} = {{\left\lbrack {PM} \right\rbrack_{A}\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix}} + {\left\lbrack {PM} \right\rbrack_{B}\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix}}}$wherein[PM]_(A) = [NPM]_(LLL)[B_(AL)] + [NPM]_(SSS)[B_(AS)]and[PM]_(B) = [NPM]_(SSS)[B_(BS)] + [NPM]_(LLL)[B_(BL)]

Knowing the normalized primary matrix for Rec2020 below:[NPM]₂₀₂₀,

the transformation from the source Rec2020 vectors to gamuts A and B arerespectively:

$\begin{bmatrix}R \\G \\B\end{bmatrix}_{A} = {{{\lbrack C\rbrack_{A}\begin{bmatrix}R \\G \\B\end{bmatrix}}_{2020}\mspace{14mu}{{where}\mspace{14mu}\lbrack C\rbrack}_{A}} = {\left\lbrack {PM} \right\rbrack_{A}^{- 1}\left\lbrack {NPM} \right\rbrack}_{2020}}$${{and}\begin{bmatrix}R \\G \\B\end{bmatrix}}_{B} = {{{\lbrack C\rbrack_{B}\begin{bmatrix}R \\G \\B\end{bmatrix}}_{2020}\mspace{14mu}{{where}\mspace{14mu}\lbrack C\rbrack}_{B}} = {\left\lbrack {PM} \right\rbrack_{B}^{- 1}\left\lbrack {NPM} \right\rbrack}_{2020}}$

As mentioned above, gamut A is used for lower luminance levels whilegamut B is utilized where applicable to achieve higher luminance levels.In contrast to the gamut scaling method, where the luminance range ofgamut A is the same across all channels, here a threshold vector isutilized as the luminance threshold, meaning that the luminance range ofgamut A varies per channel. The threshold vector representing thetransition between the ‘A’ and ‘3’ gamuts in Rec2020 space can be foundas follows:

$\begin{bmatrix}T_{R} \\T_{G} \\T_{B}\end{bmatrix}_{2020} = {\lbrack C\rbrack_{A}^{- 1}\begin{bmatrix}{0.5} \\{0.5} \\{0.5}\end{bmatrix}}$

In other words, each threshold in the threshold vector is determinedbased on a transform of the first virtual color gamut to the predefinedcolor gamut.

The following functions are then defined:f _(l)(C)=if(C<T _(C)),C,else T _(C)f _(u)(C)=C−f _(l)(C)C∈R ₂₀₂₀ ,G ₂₀₂₀ ,B ₂₀₂₀

The variable C represents the pixel values of the received video data,which is here assumed to be tristimulus Rec2020 data. Similar to thefunctions f_(l)(C) and f_(u)(C) of the gamut scaling method describedabove, the function f_(l)(C) again represents a lookup table for gamut Awhile the function f_(u)(C) represents a lookup table for gamut B. Inthe present example, the function f_(l)(C) defines a linear rampincreasing from 0 to the threshold value of the particular channel asdefined in the threshold vector and flat-lining beyond the particularthreshold value while the function f_(u)(C) defines a flat line from 0to the particular threshold value and a linear ramp increasing from theparticular threshold value. Again, here the particular threshold valuesrespectively correspond to a luminance threshold of each of the channelsof gamut A. In some embodiments, the functions f_(l)(C) and f_(u)(C) maydefine transitions other than the linear ramps described above (so longas the sum of the functions is equal to 1). For example, either or bothfunctions f_(l)(C) and f_(u)(C) may define a curve to the flat line.

For each of the pixel values of the received video data, gamut A andgamut B are derived as follows:

$\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix} = {{\begin{bmatrix}{f_{l}\left( R_{2020} \right)} \\{f_{l}\left( G_{2020} \right)} \\{f_{l}\left( B_{2020} \right)}\end{bmatrix}\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix}} = \begin{bmatrix}{f_{u}\left( R_{2020} \right)} \\{f_{u}\left( G_{2020} \right)} \\{f_{u}\left( B_{2020} \right)}\end{bmatrix}}$

In other words, for each primary channel of the incoming video dataR₂₀₂₀, G₂₀₂₀, and B₂₀₂₀, the pixel values with a luminance level underthe corresponding threshold value of the threshold vector T_(R), T_(G),and T_(B) (corresponding to a specific luminance range of gamut A) areincluded within gamut A while the pixel values that exceed theparticular threshold value (meaning that they are outside of theluminance range of gamut A) are allocated to gamut B.

Any intensity values of the derived gamut A and gamut B that arenegative values are then clipped to 0 (or white).

$\begin{matrix}{\begin{bmatrix}R_{A} \\G_{A} \\B_{A}\end{bmatrix} = \begin{bmatrix}{\max\left( {R_{A},0} \right)} \\{\max\left( {G_{A},0} \right)} \\{\max\left( {B_{A},0} \right)}\end{bmatrix}} & \lbrack 3\rbrack \\{\begin{bmatrix}R_{B} \\G_{B} \\B_{B}\end{bmatrix} = \begin{bmatrix}{\max\left( {R_{B},0} \right)} \\{\max\left( {G_{B},0} \right)} \\{\max\left( {B_{B},0} \right)}\end{bmatrix}} & \lbrack 4\rbrack\end{matrix}$

The derived gamut A and gamut B signals are then converted to thedefined primaries as described above in regard to block 308 andequations 1 and 2.

The gamut clipping method clips colors to the edge of gamuts A and Bwhich can be created approximately the same for any projector system. Inother words, colors produced by one projector may be faithfullyreproduced by any other kind of projector, regardless of whether or notthe source primaries are the same.

Alternatively, the blend function may be applied to gamuts A and Bbefore clipping the negative values. By applying the blending functionto each gamut, the values of each gamut are converted to be in terms ofthe predefined primaries of the color space of the received video data.The clipping may then be applied as shown below.

$\begin{matrix}{\begin{bmatrix}R_{L} \\G_{L} \\B_{L}\end{bmatrix} = \begin{bmatrix}{\max\left( {R_{L},0} \right)} \\{\max\left( {G_{L},0} \right)} \\{\max\left( {B_{L},0} \right)}\end{bmatrix}} \\{\begin{bmatrix}R_{S} \\G_{S} \\B_{S}\end{bmatrix} = \begin{bmatrix}{\max\left( {R_{S},0} \right)} \\{\max\left( {G_{S},0} \right)} \\{\max\left( {B_{S},0} \right)}\end{bmatrix}}\end{matrix}$

This method maximizes the gamut coverage for the particular primaries ofany projector system.

FIG. 4 illustrates a chromaticity diagram 400. The chart 400 includescolor gamuts associated with the display system 100 and the target colorgamut (here, Rec2020). Gamut 402 is the Rec2020 gamut. Gamut 404 is thegamut defined by the (long) primaries R_(L), G_(L), and B_(L) of theright eye channel (the LLL primaries) while gamut 406 is the gamutdefined by the (short) primaries R_(S), G_(S), and B_(S) of the left eyechannel (the SSS primaries). Gamut 416 is the gamut defined by drivingthe primaries of both the right eye and left eye channels with the samevalues (the “WCG” gamut). As illustrated, gamut 408 differssignificantly from the Rec2020 gamut 402. Gamut 410 is the virtual colorgamut A and gamut 412 is the virtual color gamut B. As described above,gamut A is defined as a combination of virtual primaries to approximatethe Rec2020 gamut 402 as close as possible while gamut B is defined bythe remaining energy output of the virtual primaries after the energyutilized for gamut A has been subtracted. As shown, gamut A (gamut 410)matches the Rec2020 gamut 402 more closely as compared to the summationgamut 408.

FIG. 5A illustrates a chromaticity diagram 500A including the gamuts402, 404, 406, 408, 410, and 412 described above in regard to FIG. 4.The chromaticity diagram 500A includes the input chromaticity (black)and the resulting output chromaticity (grey) achieved using the gamutclipping method described above. Lines connecting any input chromaticitypoint to an output chromaticity point (for example, the line connectinginput point 502A to output point 502B) indicate how the input color wasaltered (if needed to be). Note, in the illustrated chart 500A, themaximum input is less than the luminance threshold and thus gamut B isnot utilized and that the second clipping method described above wasused.

FIG. 5B illustrates a chromaticity diagram 500B including the gamuts402, 404, 406, 408, 410, and 412 described above in regard to FIG. 4.The chromaticity diagram 500B includes the input chromaticity (black)and the resulting output chromaticity (grey) achieved using the gamutclipping method described above. In the illustrated chart 500B, themaximum input is greater than the luminance threshold and thus gamut Bis utilized.

As mentioned above, the blending matrices are derived values determinedbased on the location of the primary compared to Rec2020. The blendmatrixes in particular are defined so as to place the short and longprimaries of the right and left eye channels respectively at aparticular desired location. Example methods to determine the blendingmatrices for each primary are described below.

FIG. 6A illustrates an enhanced view 600A of the chromaticity diagram400 of FIG. 4. As shown in the view 600A, both the short red primary RSand the long red primary R_(L) are outside of the Rec2020 color gamut402. It is necessary to bring gamut A within the Rec2020 color gamut402. To determine the blend matrix for the red primary R, one method isto bind the primary to the Rec2020 gamut. This may be done by mixing theshort red wavelength (RS) with the long green wavelength for gamut A andby mixing the short red wavelength with the long red wavelength (R_(L))for the B gamut. The distance between the long and short red wavelengthsand the Rec2020 boundary is minimized by finding the point of minimumdistance between the resulting chromaticity and the Rec2020 boundary ora point of intersection. This location is then used to define the blendmatrices. For example, the line of the enhanced view 600A represents themixture of the long red and short green wavelengths. The dot Arepresents where the mixture intersects with the Rec2020 gamut.

Another method is, in order to not be bound to the Rec2020 gamut, tomaximize the coverage of the resulting gamut. FIG. 6B illustrates anenhanced view 600B of the chromaticity diagram 400 of FIG. 4. Here, thepoint of shortest distance from a line between the blue and greenprimaries of the Rec2020 gamut to the mixture of the long red (R_(L))and short red (RS) wavelengths. This resulted in using the long red forgamut A and the short red for gamut B.

FIG. 7A illustrates an enhanced view 700A of the chromaticity diagram400 of FIG. 4. As shown in the view 700A, both the short green primaryG_(S) and the long green primary G_(L) surround the Rec2020 color gamut402. Again, it is necessary to bring gamut A within the Rec2020 colorgamut 402. Here, the primaries are bound to the Rec2020 gamut 402 bydefining an intersection point of a line B between the two greenprimaries with the Rec2020 boundary. This location is then used todefine the blend matrices. The green dot C illustrates the point atwhich the gamut A green primary lies.

Another method is, in order to not be bound to the Rec2020 gamut, tomaximize the coverage of the resulting gamut. FIG. 7B illustrates anenhanced view 700B of the chromaticity diagram 400 of FIG. 4. Here, thepoint of shortest distance from a line between the red and blueprimaries of the Rec2020 gamut to the mixture of the long green (G_(L))and short green (G_(S)) wavelengths. This resulted in using the shortgreen wavelengths.

FIG. 8A illustrates an enhanced view 800A of the chromaticity diagram400 of FIG. 4. As shown in the view 800A, both the short blue primaryB_(S) and the long blue primary B_(L) lie inside of the Rec2020 colorgamut 402. Both primaries are to be out towards the boundary of theRec2020 color gamut 402. Here, the primaries are bound to the Rec2020gamut 402 by defining an intersection point of a line D between the longblue primary and the short green wavelength with the Rec2020 boundary.This location is then used to define the blend matrices. The dot Eillustrates the point at which the gamut A blue primary lies.

Another method is to not bind the blue primaries to the Rec2020 gamut,for example, to maximize the coverage of the resulting gamut. FIG. 8Billustrates an enhanced view 800B of the chromaticity diagram 400 ofFIG. 4. Here, the point of shortest distance from a line between the redand green primaries of the Rec2020 gamut to the mixture of the long blue(B_(L)) and short green (G_(S)) wavelengths. This location is then usedto define the blend matrices. As illustrated, the long blue primary isused for gamut A while the short blue primary is used for gamut B.

In the foregoing specification, specific embodiments have beendescribed. However, one of ordinary skill in the art appreciates thatvarious modifications and changes can be made without departing from thescope of the disclosure as set forth in the claims below. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and all such modifications are intendedto be included within the scope of present teachings. For example, thetechniques disclosed herein may be applied to projection systems thatare designed for non-3D content. For instance, a dual-head projectionsystem may utilize the disclosed technology. Furthermore, the disclosedtechniques may be applied to more than two projection heads.

Moreover in this document, relational terms such as first and second,top and bottom, and the like may be used solely to distinguish oneentity or action from another entity or action without necessarilyrequiring or implying any actual such relationship or order between suchentities or actions. The terms “comprises,” “comprising,” “has”,“having,” “includes”, “including,” “contains”, “containing” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, article, or apparatus that comprises, has,includes, contains a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus. An element proceeded by“comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . .a” does not, without more constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises, has, includes, contains the element. The terms“a” and “an” are defined as one or more unless explicitly statedotherwise herein. The terms “substantially”, “essentially”,“approximately”, “about” or any other version thereof, are defined asbeing close to as understood by one of ordinary skill in the art, and inone non-limiting embodiment the term is defined to be within 10%, inanother embodiment within 5%, in another embodiment within 1% and inanother embodiment within 0.5%. The term “coupled” as used herein isdefined as connected, although not necessarily directly and notnecessarily mechanically. A device or structure that is “configured” ina certain way is configured in at least that way, but may also beconfigured in ways that are not listed.

It will be appreciated that some embodiments may be comprised of one ormore generic or specialized processors (or “processing devices”) such asmicroprocessors, digital signal processors, customized processors andfield programmable gate arrays (FPGAs) and unique stored programinstructions (including both software and firmware) that control the oneor more processors to implement, in conjunction with certainnon-processor circuits, some, most, or all of the functions of themethod and/or apparatus described herein. Alternatively, some or allfunctions could be implemented by a state machine that has no storedprogram instructions, or in one or more application specific integratedcircuits (ASICs), in which each function or some combinations of certainof the functions are implemented as custom logic. Of course, acombination of the two approaches could be used.

Moreover, an embodiment can be implemented as a computer-readablestorage medium having computer readable code stored thereon forprogramming a computer (e.g., comprising a processor) to perform amethod as described and claimed herein. Examples of suchcomputer-readable storage mediums include, but are not limited to, ahard disk, a CD-ROM, an optical storage device, a magnetic storagedevice, a ROM (Read Only Memory), a PROM (Programmable Read OnlyMemory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM(Electrically Erasable Programmable Read Only Memory) and a Flashmemory. Further, it is expected that one of ordinary skill,notwithstanding possibly significant effort and many design choicesmotivated by, for example, available time, current technology, andeconomic considerations, when guided by the concepts and principlesdisclosed herein will be readily capable of generating such softwareinstructions and programs and ICs with minimal experimentation.

Various aspects of the present invention may be appreciated from thefollowing enumerated example embodiments (EEEs):

1. A dual-head display system comprising:

a first projection head;

a second projection head;

at least one spatial modulator; and

an electronic processor configured to:

-   -   receive 2D video data;    -   generate, from the video data, a first plurality of intensity        values of virtual primaries of a first virtual color gamut and a        second plurality intensity values of a second virtual color        gamut, the first plurality of intensity values being below a        luminance threshold and approximating a predefined color gamut        and the second plurality of intensity values being above the        luminance threshold;    -   convert the first plurality of intensity values into a third        plurality of intensity values of predefined primaries of the        first projection head and the second plurality of intensity        values into a fourth plurality of intensity values of predefined        primaries of the second projection head; and    -   dynamically adjust pixel levels of the at least one spatial        modulator of the first and second projection heads based on the        third plurality of intensity values and the fourth plurality of        intensity values.        2. The system of EEE 1, wherein the luminance threshold is a        threshold vector including a threshold for each color channel of        the first virtual color gamut.        3. The system of EEE 2, wherein each threshold is determined        based on a transform of the first virtual color gamut and the        second virtual color gamut to the predefined color gamut.        4. The system of any one of EEEs 1 to 3, wherein any negative        values of the first plurality of intensity values and the second        plurality of intensity values are clipped.        5. The system of any one of EEEs 1 to 4, wherein any negative        values of the third plurality of intensity values and the fourth        plurality of intensity values are clipped.        6. A method for displaying image data, the method comprising:

receiving 2D video data;

generating, from the video data, a first plurality of intensity valuesof virtual primaries of a first virtual color gamut and a secondplurality intensity values of a second virtual color gamut, the firstplurality of intensity values of the first virtual color gamut beingbelow a luminance threshold and approximating a predefined color gamutand the second plurality of intensity values being above the luminancethreshold;

converting the first plurality of intensity values into a thirdplurality of intensity values of predefined primaries of a firstprojection head of a display system and the second plurality ofintensity values into a fourth plurality of intensity values ofpredefined primaries of a second projection head of the display system;and

dynamically adjusting pixel levels of spatial modulators of the firstprojection head and the second projection head of the display systembased on the third plurality of intensity values and the fourthplurality of intensity values.

7. The method of EEE 6, wherein the luminance threshold is a thresholdvector including a threshold for each color channel.

8. The method of EEE 7, wherein each threshold is determined based on atransform of the first virtual color gamut to the predefined colorgamut.

9. The method of any one of EEEs 6 to 8, wherein any negative values ofthe first plurality of intensity values and the second plurality ofintensity values are clipped.

10. The method of any one of EEE 6 to 9, wherein any negative values ofthe third plurality of intensity values and the fourth plurality ofintensity values are clipped.

11. The method of any one of EEE 6 to 10, wherein converting the firstplurality of intensity values into a third plurality of intensity valuesand the second plurality of intensity values into a fourth plurality ofintensity values is performed via a blending function.12. A method for displaying image data, the method comprising:

receiving video data;

generating, based on an intensity level of the video data, a firstplurality of intensity values associated with a first virtual colorgamut;

generating, based on a comparison between the intensity level and atleast one predetermined threshold, a second plurality of intensityvalues associated with a second virtual color gamut;

generating, based on the first plurality and the second plurality ofintensity values, a third plurality of intensity values and a fourthplurality of intensity values both configured to approximate apredefined color space associated with the video data; and

providing the third plurality of intensity values and the fourthplurality of intensity values to at least one spatial light modulator.

13. The method of EEE 12, wherein, in a case where the intensity leveldoes not exceed the predetermined threshold, the second plurality ofintensity values are set to zero.

14. The method of EEEs 12 or 13, wherein the second plurality ofintensity values are set based on an amount that the intensity levelexceeds the predetermined threshold, when the intensity level exceedsthe predetermined threshold.

15. The method of any one of EEEs 12 to 14, the method furthercomprising: modifying either or both of the first plurality of intensityvalues and the second plurality of intensity values when at least oneintensity value is outside of an achievable gamut volume of the firstvirtual gamut and the second virtual gamut.16. The method of any one of EEEs 12 to 15, the method furthercomprising: modifying either or both of the third plurality of intensityvalues and the fourth plurality of intensity values when at least oneintensity value is outside of an achievable gamut volume of the firstvirtual gamut and the second virtual gamut.17. The method of any one of EEEs 12 to 16, wherein the at least onepredetermined threshold is a vector based on a relationship between thefirst virtual color gamut and the second virtual color gamut in thepredefined color space.18. The method of any one of EEEs 12 to 17, the method furthercomprising defining the first virtual color gamut based on a combinationof a plurality of primary display colors associated with a light sourceto approximate a predefined color gamut associated with the predefinedcolor space, and the second virtual color gamut based on residual powerof the light source and the first virtual color gamut.19. The method of any one of EEEs 12 to 18, wherein the at least onespatial light modulator is a part of a dual-head projector.20. The method of EEE 19, wherein the dual-head projector displays a 2-Dimage based on the third plurality of intensity values and the fourthplurality of intensity values.21. A non-transitory computer-readable medium storing instructions that,when executed by a processor of a computer, cause the computer toperform operations comprising:

receiving 2D video data including tristimulus pixel values of predefinedprimaries of a predefined color space;

generating, from the video data, a first plurality of intensity valuesof virtual primaries of a first virtual color gamut and a secondplurality intensity values of a second virtual color gamut toapproximate a predefined color gamut, the first plurality of intensityvalues being below a luminance threshold of the first virtual colorgamut and the second plurality of intensity values being above theluminance threshold;

converting, via a blending function, the first plurality of intensityvalues into a third plurality of intensity values of the predefinedprimaries and the second plurality of intensity values into a fourthplurality of intensity values of the predefined primaries; and

dynamically adjusting pixel levels of at least one spatial modulator ofa dual-head projection system based on the third plurality of intensityvalues and the fourth plurality of intensity values.

What is claimed is:
 1. A dual-head display system comprising: a firstprojection head; a second projection head; at least one spatialmodulator; and an electronic processor configured to: receive 2D videodata; generate, from the video data, a first plurality of intensityvalues of virtual primaries of a first virtual color gamut and a secondplurality of intensity values of virtual primaries of a second virtualcolor gamut, the first plurality of intensity values being below aluminance threshold and approximating a predefined color gamut and thesecond plurality of intensity values being above the luminancethreshold; convert the first plurality of intensity values and thesecond plurality of intensity values into a third plurality of intensityvalues of predefined primaries of the first projection head and convertthe first plurality of intensity values and the second plurality ofintensity values into a fourth plurality of intensity values ofpredefined primaries of the second projection head; and dynamicallyadjust pixel levels of the at least one spatial modulator of the firstand second projection heads based on the third plurality of intensityvalues and the fourth plurality of intensity values; wherein theluminance threshold is a threshold vector including a threshold for eachcolor channel of the first virtual color gamut, and wherein eachthreshold is determined based on a transform of the first virtual colorgamut to the predefined color gamut.
 2. The system of claim 1, whereinany negative values of the first plurality of intensity values and thesecond plurality of intensity values are clipped.
 3. The system of claim1, wherein any negative values of the third plurality of intensityvalues and the fourth plurality of intensity values are clipped.
 4. Thesystem of claim 1, wherein the dual-head display system is configured todisplay a 2-D image based on the third plurality of intensity values andthe fourth plurality of intensity values.
 5. A method for displayingimage data, the method comprising: receiving 2D video data; generating,from the video data, a first plurality of intensity values of virtualprimaries of a first virtual color gamut and a second plurality ofintensity values of virtual primaries of a second virtual color gamut,the first plurality of intensity values of the first virtual color gamutbeing below a luminance threshold and approximating a predefined colorgamut and the second plurality of intensity values being above theluminance threshold; converting the first plurality of intensity valuesand the second plurality of intensity values into a third plurality ofintensity values of predefined primaries of a first projection head of adisplay system, and converting the first plurality of intensity valuesand the second plurality of intensity values into a fourth plurality ofintensity values of predefined primaries of a second projection head ofthe display system; and dynamically adjusting pixel levels of at leastone spatial modulator of the first projection head and the secondprojection head of the display system based on the third plurality ofintensity values and the fourth plurality of intensity values; whereinthe luminance threshold is a threshold vector including a threshold foreach color channel, and wherein each threshold is determined based on atransform of the first virtual color gamut to the predefined colorgamut.
 6. The method of claim 5, wherein any negative values of thefirst plurality of intensity values and the second plurality ofintensity values are clipped.
 7. The method of claim 5, wherein anynegative values of the third plurality of intensity values and thefourth plurality of intensity values are clipped.
 8. The method of claim5, wherein converting the first plurality of intensity values and thesecond plurality of intensity values into a third plurality of intensityvalues and converting the first plurality of intensity values and thesecond plurality of intensity values into a fourth plurality ofintensity values is performed via a blending function.
 9. The method ofclaim 5, the method further comprising: modifying either or both of thefirst plurality of intensity values and the second plurality ofintensity values when at least one intensity value is outside of anachievable gamut volume of the first virtual gamut and the secondvirtual gamut.
 10. The method of claim 5, the method further comprising:modifying either or both of the third plurality of intensity values andthe fourth plurality of intensity values when at least one intensityvalue is outside of an achievable gamut volume of the first virtualgamut and the second virtual gamut.
 11. The method of claim 5, themethod further comprising defining the first virtual color gamut basedon a combination of a plurality of primary display colors associatedwith a light source to approximate a predefined color gamut associatedwith the predefined color space, and the second virtual color gamutbased on residual power of the light source and the first virtual colorgamut.
 12. A non-transitory computer-readable medium storinginstructions that, when executed by a processor of a computer, cause thecomputer to perform operations according to claim 5.